Don't get demotivated by your first few trial exams. Getting E's/D's is inevitable in those, and it is by no means anything bad to get those grades in your first trial. I remember getting Ds/Es throughout my whole AS, not even a single grade above C, but in A2 i brought them up to A's. Just remember the grades you want will have to come with some hard work. In AS when i was getting Es/Ds i was doing the bare minimum, not even revising everyday,and if i did, it was for like 30 mins. In A2 I changed it up to 2h a day, a bit more on weekends, and the results kicked in. So remember, A-lvls are nothing like Gcses (as in how much workload you need to put in to get good grades), you need to work yo ass off to get good grades in a level, that's the harsh truth.